The present invention relates to a lasers and, more particularly, to end-pumping laser configurations.
Lasers all include three key components: (1) a pump or energy source; (2) a gain or laser medium; and (3) an optical cavity or resonator.
Two basic types of laser pumping are commonly used. In transverse pumping, or side pumping, the pumping radiation is introduced into the resonator substantially from the side while in longitudinal pumping, or end-pumping, the pumping radiation is introduced into the optical resonator substantially axially.
End (longitudinal) pumping of a laser is a well known method for generating high power high quality laser beam.
Transverse laser pumping suffers from a number of disadvantages. Transverse laser pumping could lead to an uneven spatial excitation of the lasing medium. The lack of uniformity takes place in the direction of the path of the pumping beam because of absorption, and along the axis of propagation, which is orthogonal to the pumping beam, because of the inherent pumping beam profile of the pumping source. Focusing the entire pumping laser energy onto a central spot in the optical cavity may lead to optical damage of the cavity and could leave a significant fraction of the lasing medium unexcited. See, for example, F. J. Duarte and Lloyd W. Hillman, "Dye Laser Principles", Academic Press Inc., 1990, pp 252-253, which also provides references of end-pumping developments.
Conventional end-pumping lasers also suffer from a number of disadvantages. The laser cavity, or optical resonator, typically includes an expensive dichroic mirror which has high transmission to a specific pumping wavelength and high reflectivity to a specific lasing wavelength so that conventional pumping is less commercially attractive for tunable laser where the wavelength of the laser beams is varied. In addition, the dichroic mirror and other laser components must be aligned with great precision which further adds to the cost of the laser. A further difficulty with conventional end-pumping lasers is that because of the axial alignment part of the pumping beam is reflected backward and could reach and damage the pumping source while another part of the pumping beam could exit the optical cavity along with the generated laser beam.
There is thus a widely recognized need for, and it would be highly advantageous to have, a simple and highly versatile end-pumping laser configuration which would use relatively inexpensive components, would not require extensive and highly precise alignment and would largely confine the pumping beam to the resonator, for a large variety of pumping and lasing beam wavelengths.